The invention is based on a drive device for movable structural component units, particularly in vehicles, such as window lifters, sliding-roof actuators, mirror adjusters and the like.
More particularly, it relates to a drive device for movable structural component units, which has a reversible electric motor with a rotor shaft driveable in two rotating directions, and a control device for switching on the motor in a predetermined rotating direction of the rotor shaft at switch-on command.
An example of such a drive device for movable structural component units is an electric-motor window lifter in which the desired actuating process of the side window panes of the vehicle can be triggered by actuating one of two selection switches for "window closing" and "window opening". The triggered process of "window closing" or "window opening" runs automatically as long as the respective selection switch remains actuated and is interrupted when the end position is reached by opening an end switch. The end switches have already been replaced in modern systems by electronics with Hall sensors which switch off the drive motor when the end position is reached or when there is an obstacle in the window movement path (jamming protection).
To prevent the window pane from opening automatically, e.g. due to inherent weight or shaking, it is necessary for the drive device or the structural component unit to be self-locking, which is brought about in practice by great friction in the drive motor or in the window lifter system. However, this has substantial disadvantages. On the one hand, the desired friction can be reproduced in the manufacturing process only within a very great range of dispersion, so that the drive output of the drive motor must be designed to be substantially greater than would be necessary in the isolated case in order to protect functioning. On the other hand, higher drive outputs require a correspondingly more extensive layout of lines, fuse protection, battery capacity, etc.